When a wheeled vehicle having a pair of spaced apart front wheels and/or a pair of spaced apart rear wheels turns, the frame and body of the vehicle have a tendency to roll toward the outside of the turn. In the example of a four-wheel vehicle, when the vehicle turns, the suspensions associated with the wheels on the outer side of the turn are compressed and the suspensions associated with the wheels on the inner side of the turn expand due to the weight transfer toward the outside of the turn. As a result, there is less weight on the wheels on the inside of the turn and therefore less traction provided by these wheels. The roll of the frame and body can also have an effect on the steering of the vehicle. The amount of roll/weight transfer increases as the vehicle speed increases and as the radius of curvature of the turn reduces.
In order to address the above inconveniences, some vehicles are provided with a sway bar. The sway bar connects the suspension of a wheel on one side of the vehicle with the suspension of a corresponding wheel on the other side of the vehicle. When the vehicle turns, the suspension of the wheel on the outer side of the turn is compressed. This causes torsion of the sway bar. This torsion then causes the suspension of the wheel on the inner side of the turn to also be compressed, or at least to expand less than if the sway bar was not provided. As a result, the frame and body of the vehicle roll less than if the sway bar was not provided.
Although the sway bar addresses the problems associated with the roll of the frame and vehicle body, it has some disadvantages. On such disadvantage is that the suspensions connected by the sway bar no longer act independently from each other. For example, when the right wheel of the vehicle hits a bump, the suspension of the right wheel compresses, but the sway bar also causes the suspension of the left wheel to compress even if the left wheel does not hit the bump. There are some operating conditions where independence of the suspensions may be more important than resistance to roll. For example, when a vehicle is operating at low speed over rough terrain, roll is not really an issue, but independence of the suspensions is desirable for rider comfort.
Therefore, there is a need for a suspension assembly and a vehicle having such a suspension assembly that allows selective use of the sway bar.